Nutritional intervention for improving muscular function and strength

ABSTRACT

The present invention provides a composition comprising HMB and Vitamin D. Methods of administering HMB and Vitamin D to an animal are also described. Vitamin D and HMB are administered to increase muscle mass, strength, and functionality. The combination of Vitamin D and HMB together has a synergistic effect, which results in a surprising and unexpected level of improvement in muscle mass, strength and functionality.

This application claims priority to U.S. Provisional Patent Application No. 61/121,065 filed Dec. 9, 2008 and herein incorporates the provisional patent application by reference.

BACKGROUND OF THE INVENTION

1. Field

The present invention relates to a composition comprising β-hydroxy-β-methylbutyrate (HMB) and Vitamin D, and methods of using a combination of HMB and Vitamin D to improve muscle mass, strength, or functionality.

2. Background

HMB

The only product of leucine metabolism is ketoisocaproate (KIC). A minor product of KIC metabolism is β-hydroxy-β-methylbutyrate (HMB). HMB has been found to be useful within the context of a variety of applications. Specifically, in U.S. Pat. No. 5,360,613 (Nissen), HMB is described as useful for reducing blood levels of total cholesterol and low-density lipoprotein cholesterol. In U.S. Pat. No. 5,348,979 (Nissen et al.), HMB is described as useful for promoting nitrogen retention in humans. U.S. Pat. No. 5,028,440 (Nissen) discusses the usefulness of HMB to increase lean tissue development in animals. Also, in U.S. Pat. No. 4,992,470 (Nissen), HMB is described as effective in enhancing the immune response of mammals. U.S. Pat. No. 6,031,000 (Nissen et al.) describes use of HMB and at least one amino acid to treat disease-associated wasting.

It has previous been observed that HMB alone or in combination with other amino acids is an effective supplement for restoring muscle strength and function in young athletes. Further, it has been observed that HMB in combination with two amino acids, glutamine and lysine, is effective in increasing muscle mass in elderly persons.

HMB is an active metabolite of the amino acid leucine. The use of HMB to suppress proteolysis originates from the observations that leucine has protein-sparing characteristics (1-4). The essential amino acid leucine can either be used for protein synthesis or transaminated to the α-ketoacid (α-ketoisocaproate, KIC)(1, 3). In one pathway, KIC can be oxidized to HMB. Approximately 5% of leucine oxidation proceeds via the second pathway (5). HMB is superior to leucine in enhancing muscle mass and strength. The optimal effects of HMB can be achieved at 3.0 grams per day, or 0.38 g/kg of body weight per day, while those of leucine require over 30.0 grams per day (3).

Once produced or ingested, HMB appears to have two fates. The first fate is simple excretion in urine. After HMB is fed, urine concentrations increase, resulting in an approximate 20-50% loss of HMB to urine (4, 6). Another fate relates to the activation of HMB to HMB-CoA (7-16). Once converted to HMB-CoA, further metabolism may occur, either dehydration of HMB-CoA to MC-CoA, or a direct conversion of HMB-CoA to HMG-CoA (17), which provides substrates for intracellular cholesterol synthesis. Several studies have shown that HMB is incorporated into the cholesterol synthetic pathway (12, 16, 18-20) and could be a source for new cell membranes that are used for the regeneration of damaged cell membranes (3). Human studies have shown that muscle damage following intense exercise, measured by elevated plasma CPK (creatine phosphokinase), is reduced with HMB supplementation within the first 48 hrs. The protective effect of HMB lasts up to three weeks with continued daily use (21-23).

In vitro studies in isolated rat muscle show that HMB is a potent inhibitor of muscle proteolysis (24) especially during periods of stress. These findings have been confirmed in humans; for example, HMB inhibits muscle proteolysis in subjects engaging in resistance training (4). The results have been duplicated in many studies (25) (21-23, 26-28).

The molecular mechanisms by which HMB decreases protein breakdown and increases protein synthesis have recently been reported (29-31, 31-33). In mice bearing the MAC16 cachexia-inducing tumor, HMB attenuated protein degradation through the down-regulation of key activators of the ubiquitin-proteasome pathway (30). Furthermore, HMB attenuated proteolysis-inducing factor (PIF) activation and increased gene expression of the ubiquitin-proteasome pathway in murine myotubes, thereby reducing protein degradation (31). PIF inhibits protein synthesis in murine myotubes by 50% and HMB attenuates this depression in protein synthesis (29). Eley et al demonstrated that HMB increases protein synthesis by a number of mechanisms, including the down-regulation of eukaryotic initiation factor 2 (eIF2) phosphorylation through an effect on dsRNA-dependant protein kinase (PKR) and upregulation of the mammalian target of rapamycin/70-kDa ribosomal S6 kinase (mTOR/p70^(S6k)) pathway. The net result is increased phosphorylation of 4E-binding protein (4E-BP1) and an increase in the active eIF4G.eIF4E complex. Leucine shares many of these mechanisms with HMB, but HMB appears to be more potent in stimulating protein synthesis (29).

HMB can also increase protein synthesis by attenuating the common pathway that mediates the effects of other catabolic factors such as lipopolysaccharide (LPS), tumor necrosis factor-α/interferon-γ (TNF-α/IFN-γ), and angiotensin II (Ang II) (32, 33). HMB acts by attenuating the activation of caspases-3 and -8, and the subsequent attenuation of the activation of PKR and reactive oxygen species (ROS) formation via down-regulation of p38 mitogen activated protein kinase (p38MAPK). Increased ROS formation is known to induce protein degradation through the ubiquitin-proteasome pathway. HMB accomplishes this attenuation through the autophosphorylation PKR and the subsequent phosphorylation of eIF2α, and in part, through the activation of the mTOR pathway.

Numerous studies have shown an effective dose of HMB to be 3.0 grams per day as CaHMB (˜38 mg/kg body weight-day⁻¹). This dosage increases muscle mass and strength gains associated with resistance training, while minimizing muscle damage associated with strenuous exercise (34) (4, 23, 26). HMB has been tested for safety, showing no side effects in healthy young or old adults (35-37). HMB in combination with L-arginine and L-glutamine has also been shown to be safe when supplemented to AIDS and cancer patients (38).

Studies in humans have also shown that dietary supplementation with 3 grams of CaHMB per day plus amino acids attenuates the loss of muscle mass in various conditions such as cancer and AIDS. (3, 4, 26, 34, 39, 40) A meta-analysis of supplements to increase lean mass and strength with weight training showed HMB to be one of only 2 dietary supplements that increase lean mass and strength with exercise (34). More recently it was shown that HMB and the amino acids arginine and lysine increased lean mass in a non-exercising, elderly population over a year-long study.

Vitamin D

Vitamin D has classically been associated with calcium and phosphorous metabolism and bone strength. Until recently, an adequate Vitamin D level has been defined using the Vitamin D deficiency disease rickets. While 1,25OH₂-VitD₃ is the active metabolite of Vitamin D, a measure of Vitamin D status widely accepted is serum (blood) circulating 25-OH VitD₃. A circulating blood level between 10 and 15 ng 25-OH VitD₃/mL will cause rickets in young children and has been accepted as the deficiency level for Vitamin D. Vitamin D can be synthesized by humans with adequate sun exposure or can be obtained through the diet and through supplements to the diet. Many factors influence the amount and effectiveness of Vitamin D found in the body. These factors include dietary intake, sun exposure, Vitamin D receptor number (VDR), conversion rate from cholecalciferol to 25OHD and finally the conversion of 25-OH VitD₃ to 1,25OH₂-VitD₃.

Most of the population in northern latitudes (most of the United States) do not produce Vitamin D in the winter regardless of sun exposure because the sun's ultraviolet B rays do not reach the earth during that time and therefore the only source of Vitamin D is dietary (42). As the 25 hydroxylation occurs in the liver and the 1 hydroxylation occurs primarily in the kidney, these two organs play a large role in determining the circulating levels of Vitamin D, and the functioning of these organs and thus Vitamin D status tends to decrease with age (42).

In a recent review, Holick details research showing that circulating levels of 25-OH VitD₃ must reach as high as 30-40 ng/mL before parathyroid hormone (PTH) levels begin to plateau (43). Other researchers have found that increasing 25-OH VitD₃ from 20 to 32 ng/mL increased intestinal calcium transport (44). Both of these criteria would point to a 25-OH VitD₃ level of 30 ng/mL or greater being required for optimal regulation of calcium metabolism in the body. A recent review by Heaney describes the optimal level of 25-OH VitD₃ to be 32 ng/mL or greater for optimal health which takes into account a number of aspects other than bone health and calcium metabolism (45). By these standards, from 40 to 100% of independent elderly men and women are Vitamin D deficient (43).

The 1-alpha, 25-Vitamin D hydroxylase in the kidney has been considered the primary source for synthesis of the circulating active metabolite of Vitamin D, 1,25OH₂-VitD₃. The activity of this enzyme is regulated on a whole body level by parathyroid hormone (PTH). Regulating 1,25OH₂-VitD₃ on a whole body level probably does not provide for optimal levels of the active vitamin for all body tissues at one time. Relatively recently tissue specific 1-alpha, 25-Vitamin D hydroxylases have been identified and are thought to mediate autocrine responses of Vitamin D at the tissue specific level (46, 47). Human vascular smooth muscle has 1-alpha, 25-Vitamin D hydroxylase activity with a Km of 25 ng/mL. This means that the enzyme is operating at one half maximal capacity at a 25-OH VitD₃ concentration of 25 ng/mL (48). Therefore serum levels of >25 ng/mL may be necessary for optimal active Vitamin D for vascular smooth muscle cells.

Muscle strength declines with age and a recently characterized deficiency symptom of Vitamin D is skeletal muscle weakness (43). Deficiency of Vitamin D and its hormonal effect on muscle mass and strength (sarcopenia) has been described as a risk factor in falls and bone fractures in the elderly (49). Loss of muscle strength has been correlated with a loss of Vitamin D receptors (VDR) in muscle cells (50). Supplemental Vitamin D of at least 800 IU per day may result in a clinically significant increase in VDR in muscle cells which may be in part be the mechanism whereby other studies have shown improvement in body-sway, muscle strength and falling risk were seen with Vitamin D supplementation at this level (51). While this muscular weakness associated with Vitamin D may not be surprising at classical Vitamin D deficiency levels (blood 25OH-VitD₃ of <15 ng/mL), Bischoff-Ferrari et al continued to see improvement in lower extremity function up to and beyond 40 ng 25-OH VitD₃/mL which are levels well above what previously might have been thought necessary for maximal benefit (52). This observation has been confirmed by other researchers that in fact minimal Vitamin D levels necessary to prevent rickets do not allow for maximal physical performance (53). A recent editorial in American Journal of Clinical Nutrition stated that all the literature available would indicate a 25OH-VitD₃ level of at least 30 ng/mL is most optimal for health and disease (54).

While the exact mechanism is still unclear, it is clear that both the active metabolite, 1,25OH₂-VitD₃ and its precursor, 25-OH VitD₃, play a significant role in normal functioning of muscle. Muscle contains VDRs for 1,25OH₂-VitD₃, found in both the nucleus and at the cell membrane (55-57) and these are also involved in non-specific binding 25-OH VitD₃ as well (58). Studies by Haddad and Birge, published in the 1970s, show that feeding D₃ to vitamin D deficient rats 7 hours prior to measurement increased protein synthesis as measured by ³H-leucine incorporation into muscle cell proteins. However, when the muscles were removed from the Vitamin D deficient rats and studied, only 25-OH Vit D₃ acts directly in the muscles (58-60).

Early clinical evidence pointed to a reversible myopathy associated with Vitamin D deficiency (61). Vitamin D receptors were discovered in muscle tissue, thus providing direct evidence of Vitamin D's effect on muscle function (51, 62). Muscle biopsies in adults with Vitamin D deficiency exhibit mainly type II muscle fiber atrophy (63). Type II fibers are important because they are the first initiated to prevent a fall. A recent randomized controlled study found that daily supplementation of 1,000 IU of Vitamin D₂ in elderly stroke survivors resulted in an increase in mean type II fiber diameter and in percentage of type II fibers (64). There was also a correlation between serum 25-OH VitD₃ level and type II fiber diameter.

Vitamin D conveys its action by binding to VDR. VDR is expressed in particular stages of differentiation from myoblast to myotubes (55, 65, 66). Two different VDRs have been described. One is located at the nucleus and acts as a nuclear receptor and the other is located at the cell membrane and acts as a cellular receptor. VDR knockout mice are characterized by a reduction in both body weight and size as well as impaired motor coordination (67). The nuclear VDR is a ligand-dependent nuclear transcription factor that belongs to the steroid-thyroid hormone receptor gene superfamily (68). Bischoff et al (69) reported the first in situ detection of VDR in human muscle tissue with significant associated intranuclear staining for VDR. Once 1,25OH₂-VitD₃ binds to its nuclear receptor, it causes changes in mRNA transcription and subsequent protein synthesis (70). The genomic pathway has been known to influence muscle calcium uptake, phosphate transport across the cell membrane, phospholipid metabolism, and muscle cell proliferation and differentiation. 1,25OH-VitD₃ regulates muscle calcium uptake by modulating the activity of calcium pumps in sacroplasmic reticulum and sacrolemma (61). Modifications of calcium levels impact muscle function (71). In vitro experiments support these findings by demonstrating an increased uptake of ⁴⁵Ca in cells exposed to physiological levels of 1,25OH₂-VitD₃ (72). The calcium binding protein calbindin D-9K is synthesized as a result of activation of nuclear VDR (62). 1,25OH₂-VitD₃ plays a role in regulating phosphate metabolism in myoblasts by accelerating phosphate uptake and accumulation in cells. 1,25OH₂-VitD₃ acts rapidly, presumably through cell membrane VDRs (56, 57). While binding to these receptors, there is an activation of second-messenger pathways (G-proteins, cAMP, inositol triphosphate, arachidonic acid) (73-75) or the phosphorylation of intracellular proteins. These would in turn activate protein kinase C(PKC), leading to release of calcium into muscle cells, and ultimately resulting in active transport of Ca into the sacroplasmic reticulum by Ca-ATPase. This process is important for muscle contraction. Additionally, PKC affects enhancements of protein synthesis in muscle cells (76). Recent data (77) indicate that 1,25-OH VitD₃ has a fast activation of mitogen-activated protein kinase (MAPK) signaling pathways, which in turn forward signals to their intracellular targets that effect the initiation of myogenesis, cell proliferation, differentiation, or apoptosis.

Vitamin D may also regulate formation and regeneration of tight junctions and neuromuscular junctions. In vitro studies that found that Vitamin D regulates expression of VDR and the neural growth factor (NGF) in Schwann cells (78). Recent studies have shown that Vitamin D enhances glial cell line-derived neurotrophic factor (GDNF) in rats and that this may have beneficial effects in neurodegenerative disease (79). Therefore, Vitamin D could act through several mechanisms of cellular function and neural interaction to improve overall muscle strength and function.

A need exists for a composition and methods to increase muscle mass and improve function and strength. The present invention comprises a composition and methods of using a combination of Vitamin D and HMB that results in such an increase in muscle mass and improvement in strength and function.

SUMMARY OF THE INVENTION

One object of the present invention is to provide a composition for increasing muscle mass, strength, or functionality.

Another object of the present invention is to provide methods of administering a composition for increasing muscle mass, strength or functionality.

These and other objects of the present invention will become apparent to those skilled in the art upon reference to the following specification, drawings, and claims.

The present invention intends to overcome the difficulties encountered heretofore. To that end, a composition comprising HMB and Vitamin D is provided. The composition is administered to a subject in need thereof to increase muscle mass, strength and functionality. All methods comprise administering to the animal HMB and Vitamin D.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is a graph showing the changes in muscle mass in subjects depending on Vitamin D status.

FIG. 1 b is a graph showing overall knee strength based on Vitamin D status with administration of HMB.

FIG. 2 a is a graph showing serum Vitamin D levels in subjects.

FIG. 2 b is a graph showing knee extension strength in subjects.

FIG. 2 c is a graph showing an eight week performance index in subjects.

FIG. 3 shows the Protein:DNA ration and protein degradation in C₂C₁₂ cells.

FIG. 4 a is a graph showing serum Vitamin D levels in subjects.

FIG. 4 b is a graph showing urine HMB excretion in subjects.

DETAILED DESCRIPTION OF THE INVENTION

The present invention comprises a combination of HMB and Vitamin D that has a synergistic effect and improves overall muscle strength and function. The combination of HMB and Vitamin D results in significant enhancements in overall muscle mass, function and strength. This combination can be used on all age groups seeking enhancement in overall muscle mass, function and strength. The following methods describe and show increased overall muscle mass, function and strength even in non-exercising animals.

One specific use HMB and Vitamin D is in the older or elderly population. Current estimates place a large portion of the older population at risk for falls with potential significant associated morbidities. The combination of HMB and Vitamin D specifically targets muscle mass, strength and function and consequently may produce significant improvement in health, quality of life, and in particular, decreased falls and injury in this group.

The younger population also benefits from the administration of HMB and Vitamin D, in part due to the widespread occurrence of Vitamin D deficiency. Women also benefit from the administration of HMB and Vitamin D as women are prone to Vitamin D deficiency.

The present invention provides a composition comprising HMB and Vitamin D. The composition is administered to an animal in need of improvement in overall muscle mass, strength or function.

The composition of HMB and Vitamin D is administered to an animal in any suitable manner. Acceptable forms include, but are not limited to, solids, such as tablets or capsules, and liquids, such as enteral or intravenous solutions. Also, the composition can be administered utilizing any pharmaceutically acceptable carrier. Pharmaceutically acceptable carriers are well known in the art and examples of such carriers include various starches and saline solutions. In the preferred embodiment, the composition is administered in an edible form.

B-hydroxy-β-methylbutyric acid, or β-hydroxy-isovaleric acid, can be represented in its free acid form as (CH₃)₂(OH)CCH₂COOH. The term “HMB” refers to the compound having the foregoing chemical formula, in both its free acid and salt forms, and derivatives thereof. While any form of HMB can be used within the context of the present invention, preferably HMB is selected from the group comprising a free acid, a salt, an ester, and a lactone. HMB esters include methyl and ethyl esters. HMB lactones include isovalaryl lactone. HMB salts include sodium salt, potassium salt, chromium salt, calcium salt, magnesium salt, alkali metal salts, and earth metal salts.

Methods for producing HMB and its derivatives are well-known in the art. For example, HMB can be synthesized by oxidation of diacetone alcohol. One suitable procedure is described by Coffman et al., J. Am. Chem. Soc. 80: 2882-2887 (1958). As described therein, HMB is synthesized by an alkaline sodium hypochlorite oxidation of diacetone alcohol. The product is recovered in free acid form, which can be converted to a salt. For example, HMB can be prepared as its calcium salt by a procedure similar to that of Coffman et al. in which the free acid of HMB is neutralized with calcium hydroxide and recovered by crystallization from an aqueous ethanol solution. The calcium salt of HMB is commercially available from Metabolic Technologies, Ames, Iowa.

Vitamin D is present in the composition in any form. In the preferred embodiment, Vitamin D₃ (cholecalciferol) is administered, but the invention is not limited to that form of Vitamin D. While Vitamin D₃ is the synthesized and preferred form of Vitamin D for mammals, mammals can also use supplemental Vitamin D₂. Vitamin D2 may be less potent than Vitamin D₃, hence additional D₂ may be required in order to raise blood levels of 25-OH VitD₂.

When the composition is administered orally in an edible form, the composition is preferably in the form of a foodstuff or pharmaceutical medium, more preferably in the form of a foodstuff. Any suitable foodstuff comprising the composition can be utilized within the context of the present invention. In order to prepare the composition as a foodstuff, the composition will normally be blended with the appropriate foodstuff in such a way that the composition is substantially uniformly distributed in the foodstuff. Alternatively, the composition can be dissolved in a liquid, such as water. Although any suitable pharmaceutical medium comprising the composition can be utilized within the context of the present invention, preferably, the composition is blended with a suitable pharmaceutical carrier, such as dextrose or sucrose, and is subsequently tabulated or encapsulated as described above.

Furthermore, the composition can be intravenously administered in any suitable manner. For administration via intravenous infusion, the composition is preferably in a water-soluble non-toxic form. Intravenous administration is particularly suitable for hospitalized patients that are undergoing intravenous (IV) therapy. For example, the composition can be dissolved in an IV solution (e.g., a saline or glucose solution) being administered to the patient. Also, the composition can be added to nutritional IV solutions, which may include amino acids and/or lipids. The amounts of the composition to be administered intravenously can be similar to levels used in oral administration. Intravenous infusion may be more controlled and accurate than oral administration.

Methods of calculating the frequency by which the composition is administered are well-known in the art and any suitable frequency of administration can be used within the context of the present invention (e.g., one 6 g dose per day or two 3 g doses per day) and over any suitable time period (e.g., a single dose can be administered over a five minute time period or over a one hour time period, or, alternatively, multiple doses can be administered over an eight week time period). The combination of HMB and Vitamin D can be administered over an extended period of time, such as months or years.

It will be understood by one of ordinary skill in the art that HMB and Vitamin D do not have to be administered in the same composition to perform the claimed methods. Stated another way, separate capsules, pills, mixtures, etc. of Vitamin D and of HMB may be administered to a subject to carry out the claimed methods.

Any suitable dose of HMB can be used within the context of the present invention. Methods of calculating proper doses are well known in the art. The dosage amount of HMB can be expressed in terms of corresponding mole amount of Ca-HMB. The dosage range within which HMB may be administered orally or intravenously is within the range from 0.01 to 0.2 grams HMB (Ca-HMB) per kilogram of body weight per 24 hours. For adults, assuming body weights of from about 100 to 200 lbs., the dosage amount orally or intravenously of HMB (Ca-HMB basis) can range from 0.5 to 30 grams per subject per 24 hours.

The amount of Vitamin D in the composition can be selecting an amount of Vitamin D within the range of greater than 500 IU, as the below examples indicate that 500 IU is the lower threshold for an effective amount in individuals with inadequate levels of Vitamin D in their bloodstream, yet not too much Vitamin D as to be toxic. Further, the composition may include Vitamin D in amounts sufficient to raise blood levels of Vitamin D to at least around 25 ng/ml.

In the preferred embodiment, the composition comprises HMB in the form of its calcium salt, and Vitamin D in the form of 25-0H Vit D₃. Preferably, a composition in accordance with the present invention comprises HMB in an amount from about 0.5 g to about 30 g and 25-0H VitD in an amount greater than 500 IU, but not in an amount high enough to be toxic. One range of Vitamin D in accordance with this invention is around 1000 IU to around 4000 IU. For examples, 1001 IO, 1002 IU, 1003 IU . . . 1995 IU, 1996 IU, 1997 IU, 1998 IU, 1999 IU, 2000 IU, 200 HU, 2002 IU, 2003 IU, 2004 IU, 2005 IU . . . 3997 IU, 3998 IU, 3999 IU, and all numbers between around 1000 IU and 4000 IU and not otherwise stated.

In an additional embodiment, the composition in accordance with the present invention comprises HMB in an amount from about 0.5 g to about 30 g and Vitamin D in an amount sufficient to increase circulating blood levels of 25-OH VitD₃ or 25-OH VitD₂, depending on the form supplemented, to at least about 25 ng/ml.

In general, an amount of HMB and vitamin in the levels sufficient to improve overall muscle strength, function, and overall mass is administered for an effective period of time.

The invention provides a method of administering a composition of HMB and Vitamin D to an animal such that the animal's muscle mass increases. The animal may or may not engage in exercise. Exercising in conjunction with the administration of HMB and Vitamin D results in an even greater improvement in strength and muscle function, but exercise is not necessary to improve strength and muscle function. The amount of HMB and Vitamin D in the composition administered that are effective for increasing the animal's muscle mass can be determined in accordance with methods well-known in the art. In one embodiment, the effective amount of HMB in the composition may be from about 0.5 g to about 30 g and the effective amount of Vitamin D in the composition may be from greater than about 500 IU per 24 hour period. In another embodiment, the effective amount of HMB is the same, and the effective amount of Vitamin D is that which is sufficient to increase blood levels of Vitamin D to at least about 25 ng/ml.

The invention provides a method of administering a composition of HMB and Vitamin D to an animal such that the animal's strength increases. The animal may or may not engage in exercise. The amount of HMB and Vitamin D in the composition administered that are effective for increasing the animal's muscle mass can be determined in accordance with methods well-known in the art. In one embodiment, the effective amount of HMB in the composition may be from about 0.5 g to about 30 g and the effective amount of Vitamin D in the composition may be from greater than about 500 IU per 24 hour period. In another embodiment, the effective amount of HMB is the same, and the effective amount of Vitamin D is that which is sufficient to increase blood levels of Vitamin D to at least about 25 ng/ml.

The invention further comprises a method of administering a composition of HMB and Vitamin D in an effective amount for improving muscle function. The amount of HMB and Vitamin D in the composition administered that are effective for increasing the animal's muscle mass can be determined in accordance with methods well-known in the art. In one embodiment, the effective amount of HMB in the composition may be from about 0.5 g to about 30 g and the effective amount of Vitamin D in the composition may be from greater than about 500 IU. In another embodiment, the effective amount of HMB is the same, and the effective amount of Vitamin D is that which is sufficient to increase blood levels of Vitamin D to at least about 25 ng/ml.

EXAMPLES

The following examples further illustrate the invention but should not be construed as in any way limiting its scope. For example, the amounts of HMB and Vitamin D administered and the duration of the supplementation are not limited to what is described in the examples.

These examples demonstrate the surprising result that the combination of vitamin D and HMB improves strength and muscle function. It was previously known that HMB supplementation increases muscle mass, but no corresponding improvement in strength and muscle function was seen with HMB alone. The examples demonstrate that when serum levels of Vitamin D reach appropriate levels, most typically through supplementation, muscle strength and function improve.

Example 1

It is known that administration of HMB and amino acids, specifically arginine and lysine, administered to the non-exercising population results in significant increases in lean mass and improvement in protein turnover. Due to the increases in lean mass and improvement in protein turnover, it would be expected that administration of HMB and amino acids would also improve strength and function. Administration of HMB and amino acids alone, however, does not result in improvement in strength, function, or both. Instead, a gradual loss of handgrip and leg strength is observed. The following example demonstrates that the amount of Vitamin D in the bloodstream affects whether administration of HMB shows improvement in muscle strength and/or function. The data demonstrate that administration of HMB, arginine, and lysine (HMB/ARG/LYS) and Vitamin D is superior to administration of either HMB/ARG/LYS alone or Vitamin D alone. These results show a synergistic effect between HMB and Vitamin D for improving muscle strength and function.

Methods

The effects of HMB, arginine, and lysine (HMB/ARG/LYS) on strength and muscle function in the elderly was studied in both elderly men (n=38) and women (n=39) with an average age of 76.0±1.6 years (80). Subjects were randomly assigned to either treatment with HMB/ARG/LYS (n=40) or to an isonitrogenous control group (n=37) for a one year study. Supplements were taken once per day in the morning with breakfast and all supplements supplied 0.1 g ascorbic acid per day. The HMB/ARG/LYS contained 2 g CaHMB, 5 g arginine, and 1.5 g lysine. The control contained 5.6 g alanine, 0.9 g glutamic acid, 3.1 g glycine, and 2.2 g serine. The supplements were supplied as a ready to mix orange-flavored powder. Subjects weighing more than 68 kg were given supplements containing 1.5 times the dosage above to maintain close to 38 mg/kg body weight per day CaHMB intake as this has been shown to be an effective intake of HMB per day. Lean tissue mass was measured using two independent methods, bioelectrical-impedance analysis (BIA) and dual energy x-ray absorptiometry (DXA). Strength was measured in the upper and lower extremities.

The retrospective analysis of serum 25-OH VitD₃ in the same cohort was performed and the data were stratified based upon the Vitamin D status of the subjects within each original treatment group. An “adequate Vitamin D status” was defined as serum 25-OH VitD₃ level of ≧30 ng/mL (82-84). Consequently four cohorts were identified: (1) control-subjects with a 25-OH VitD₃ level <30 ng/mL (n=25); (2) HMB/ARG/LYS subjects with a 25-OH VitD₃ level <30 ng/mL (n=29); (3) control subjects with a 25-OH VitD₃ level >30 ng/mL (n=12); and (4) HMB/ARG/LYS subjects with a 25-OH VitD₃ level >30 ng/mL (n=11).

Statistics

The data, means and changes in means over the 12-month period, were analyzed using a mixed models procedure of the Statistical Analysis System for Windows (Release 8.02, SAS Institute, Cary, N.C.). A repeated measures analysis of variance (ANOVA) that included the initial time 0 values for the variable measured as a covariate and main effects of site, gender, and treatment. Lean body mass was analyzed using linear and quadratic time by treatment contrasts.

Results and Analysis

Supplementation with HMB/ARG/LYS resulted in statistically significant increases in muscle mass irrespective of the Vitamin D status. The 12-month increase in lean mass within the cohorts with 25-OH VitD₃>30 ng/mL was 0.9 kg, and 0.7 kg in the cohorts with <30 ng/mL (FIG. 1 a, p=0.02), which were not significantly different. However, regardless of Vitamin D status, there was a significant increase in lean mass over the year long supplementation (FIG. 1 a, p=0.02). On the other hand there was significant divergence in muscle strength based upon Vitamin D status (FIG. 1 b). Measurements of “Overall Knee Strength” showed that the HMB/ARG/LYS-supplemented group with 25-OH VitD₃ level >30 ng/mL had significant improvements in muscle strength. When this group was compared with the other three cohorts, there was a 21% linear increase in strength (p<0.003).

Taken together, these results suggest a synergistic effect between the HMB-supplemented cocktail and Vitamin D. Although HMB/ARG/LYS supplementation increased muscle mass (fat-free-mass) regardless of Vitamin D status, strength was only increased with HMB/ARG/LYS supplementation when subjects had adequate Vitamin D status.

The combination of HMB/ARG/LYS and adequate Vitamin D status is necessary for and superior to either HMB/ARG/LYS alone or adequate Vitamin D alone based upon the controls with adequate Vitamin D in improving the strength and functionality of muscle. These results show a synergistic effect between HMB and Vitamin D for improving muscle strength and function.

Prior studies examining the effect of HMB on increasing muscle mass were not significantly improved in all study designs (published and unpublished). It is believed that Vitamin D status may not have been adequate to maximize muscle mass gains in these earlier studies in the HMB-supplemented subjects. This may be especially true in populations where low vitamin D status due to age, geographical location, dietary intake, or disease was in question. Consequently, supplementation with a combination of HMB and Vitamin D may not only increase muscle strength and functionality but also restore or increase muscle mass compared to supplementation of HMB alone.

Example 2

In this example, subjects were administered a combination of HMB and vitamin supplements.

Materials and Methods:

Elderly women (n=30) and men (n=16) were recruited into a double-blinded controlled study. The older adults were recruited from two locations in South Dakota: Brookings and Sioux Falls. The subjects underwent an initial screening and were randomized to treatments. Testing consisted of an initial (0 weeks) and follow-up testing at 4, 8 and 12 weeks over the course of the 12-week study.

Prior to the start of the experimental period, we randomly assigned nutritional supplements to each subject using computer-generated random numbers in a double-blind fashion. Treatments were arranged in a 2×2 factorial design with two levels of HMB (0 & 3.0 g/d) and two levels of Vitamin D (0 & 2,000 IU/d). We assigned subjects to one of the following four treatments:

(1) Control

(2) HMB (calcium salt), 3.0 g/day

(3) 2,000 IU Vitamin D/day

(4) HMB, 3.0 g/day+2,000 IU Vitamin D.

The treatments were supplied in capsules of equal size and color and contained equal amounts of calcium and phosphorus. The subjects were instructed to take three capsules two times a day. Each subject was supplied with a one-week supply of the supplement, allocated by subject number and returned each week for an additional 1-week supply.

The exercise testing and training session was supervised by trained research associates. Resting heart rate and blood pressure measurements were obtained prior to strength measurements. Enrolled individuals participated in an exercise training program consisting of strength training exercises with Theraband® stretch cords (resistance training) and jumping. The equipment consisted of items that can easily be used at home. Exercise sessions were 3 times a week for 12 weeks. Each exercise session was about 45-60 minutes. Testing sessions were performed at 0, 4, 8, and 12 weeks. Each testing session lasted ˜60 minutes.

The strength program incorporated the following exercises: bicep curls, triceps extensions, chair squats, calf raises, ankle dorsiflexion, shoulder front raises and lateral raises, latissimus dorsi pull-down, chest press, seated row, knee flexion and extension, and hip flexion. For each of the 12 exercises, the participants completed 3 sets of isotonic movement, 2 sets of 20 repetitions, and a final set to failure. When the 3^(rd) set could be performed for 20 repetitions in good form, the resistance was increased by moving to the next color of the resistance band. Between each set, participants performed a set of hops or small jumps. Initially, 5 hops/jumps were performed following each set. The number of hops/jumps was increased by 5 every 3 weeks until 25 hops/jumps were achieved. Subjects remained at 25 hops/jumps between sets for the remainder of the study. The number of hops/jumps was reduced or omitted if there are any complaints regarding joint pain. The resistance bands had been shown to safely increase strength and functionality when used in an older adult population (87-90).

Body composition measurements were obtained at 0, 4, 8, and 12 weeks. Measurements of strengths of quadriceps (extension/flexion) and elbows (extension/flexion) were obtained using the BIODEX Isokinetic Dynamometer. Handgrip strength was measured using a handgrip dynamometer. Peak torque for knee extension and flexion was measured at 60, 90 and 120°/sec. Peak torque for elbow extension and flexion was measured at 60 and 120°/sec.

Functionality tests included: “Get-up-and-Go” performance (speed and gate), and “Get-up” performance. The “Get-up-and-Go” test consisted of timed measurements of the subject's starting from a seated position, standing, walking forward 3 meters, turning around, walking back to the chair, and sitting down. The “Get-up” test consisted of the subject standing upright from a seated position as many times as possible within 30 seconds. The complete descriptions and standardization of the tests are outlined in the Physical Dimensions of Aging by Waneen W. Spirduso (Human Kinetics, 1995).

A muscular performance index was calculated by summing the percentage change from baseline for Get-up-and-Go, Get-up, handgrip, peak torque for knee extension and flexion (60, 90 and 120°/sec) and peak torque for elbow extension and flexion (60°/sec).

At 0, 4, 8, and 12 weeks blood samples were taken from a superficial arm vein into Vacutainers™ (Becton Dickinson, Vacutainer Systems, Rutherford, N.J.) after an overnight fast. Serum was collected and used to measure 25-OH VitD₃ using a fully automated antibody-based chemiluminescence assay (DiaSorin Inc., Stillwater, Minn.).

Least Squares Mean±SEM were calculated strength and functionality changes in each variable over the 12-week period. The mixed models procedure of the Statistical Analysis System for Windows (Release 9.1, SAS Institute, Cary, N.C.) was used to analyze the data. Analysis of Covariance was used with main effects of HMB, Vitamin D and the HMB*Vitamin D interaction. Data were adjusted using the initial serum 25-OH VitD₃ concentration as the covariate. The hypothesize was that the combination of HMB and Vitamin D supplementation will result in a greater improvements in strength and functionality as compared to control, HMB, or Vitamin D-treated subjects. This synergistic effect was tested with pre-planned one-tail t-test in a post-hoc analysis. Statistical significance was determined for p<0.05 and a trend was determined for 0.05<p<0.10.

Results and Discussion:

A total of 43 subjects completed the 12-week and one subject completed the 8-weeks of the study and was included in the analysis. Two subjects dropped from the study prior to the 4-week follow-up visit and were not used in the analysis. The subjects that dropped from the study did so because of the demanding commitment of a 12-week training study and not due to any adverse events. The subject characteristics of the 44 subjects used in the analysis are presented in Table 1.

TABLE 1 Subject Characteristics Item Control HMB VitD₂₀₀₀ HMB + VitD₂₀₀₀ n 11 11 11 11 Age 73.4 ± 2.6 73.5 ± 3.0 72.1 ± 2.8 68.5 ± 2.5 (62-87) (60-89) (61-96) (60-84) M/F 3/8 4/7 4/7 4/7 *250H- 29.2 ± 3.0 25.4 ± 3.0 24.0 ± 2.0 27.4 ± 3.0 VitD₃ (12.4-46.5) (12.2-39.7) (11.7-34.3) (15.1-42.9) #Leg 73.9 ± 9.6 64.1 ± 7.4  74.8 ± 10.0  83.1 ± 10.6 Strength, Extension  (33-148)  (23-98.3) (24.7-133)   (40.5-146.1) Flexion 51.4 ± 6.2 43.6 ± 5.3 55.9 ± 6.1 51.8 ± 7.7 (23-95) (14-61) (13.8-83)  (18-99) Data are expressed as Mean ± SE (min-max) *Baseline value #Baseline Peak Torque @ 60°/sec The average 25-OH VitD₃ concentration at wk 0 was 26.5 ng/ml. Subjects treated with 2000 IU of Vitamin D per day increased their serum 25-OH VitD₃ level by 10.7 ng/mL (FIG. 2 a). However, subjects either supplemented with a control or HMB alone decreased their serum 25-OH VitD₃ level by 2.0 ng/mL. A clean catch urine sample was used to test for supplement compliance. Subjects supplemented with HMB had a 50 fold increase in urinary HMB concentration whereas the subjects not consuming a HMB supplement had no increase urinary HMB concentration.

The effects of the combination of HMB and Vitamin D on knee extension strength (peak torque, 60°/sec is presented in FIG. 2 b. Supplementation with HMB+Vitamin D (7.28±5.03 nm) in older adults results in a statistically greater eight week increase in knee extension strength as compared to control-treated subjects, P<0.05 (−6.28±5.02 nm). Neither the HMB alone nor the Vitamin D-treated subjects increased knee extension strength when compared to the control-treated subjects. These data support our hypothesis that the combination of HMB+Vitamin D would be synergistic on muscular strength.

Although not significant the performance index tends supports these observations (see FIG. 2 c). The performance index not only includes leg strength measurements but also functionality, hand grip strength, and elbow strength. These strength and function measurements are summed into one overall performance index. The combination of HMB+Vitamin D resulted in a 146% increase in the performance index over the control. Whereas HMB and Vitamin D supplementation resulted in only a 35 and 58% increase, respectively, when compared to older adults supplemented with the control treatment.

Implications:

These data from a prospective study in older adults support the hypothesis that the combination of HMB and Vitamin D supplementation is synergistic, and resulted in significant improvements in knee muscle strength and overall performance index. These data support the observation from our retrospective study in an elderly population supplemented with HMB, Arginine, and Lysine. Muscular strength increases only occur with HMB, Arginine, and Lysine in older adults with adequate Vitamin D. In conclusion, the combination HMB and Vitamin D is superior to either HMB or Vitamin D alone and is therefore synergistic. These findings are important as the Vitamin D status in approximately 66% of the elderly population is low and leads to a decrease in muscular strength and function. The loss of strength and function leads to an increase in falls and fractures, poor quality of life and will ultimately impact health care costs.

Example 3

In this example, cell culture studies were performed to analyze the effects of HMB and vitamin D on protein, DNA and protein turnover in muscle cell cultures.

Recent in vitro studies have shown that HMB decreases protein breakdown. In one study HMB attenuated proteolysis-inducing factor (PIF) activation and increased gene expression of the ubiquitin-proteasome pathway in murine myotubes, thereby reducing protein degradation (91). Other studies also suggest HMB may influence protein synthesis through the mTOR pathway (92). Early studies have also suggested that vitamin D affects protein metabolism (93). Vitamin D also binds a VDR found in the nucleus of muscle cells and regulates gene expression (94). We hypothesize that HMB and vitamin D both have effects on muscle cells and that if they act through independent mechanisms there could be a synergistic effect on either protein, DNA or protein turnover in the cells.

Methods

Mouse C2C12 skeletal muscle cell myoblasts were grown in culture under standard conditions and fused into myotubes following the methods of Menconi et al. (95). Four separate studies were conducted during different weeks. The first 3 studies consisted of 4 replicate dishes per treatment and the fourth study consisted of 6 replicate dishes per treatment. The treatments were applied to the cells during the 24 h measurement period. Treatments applied were control, 25-OH VitD₃ (200 ng/mL), HMB (200 μM HMB as Ca(HMB)₂, and the combination of HMB and 25-OH VitD₃. Dexamethasone (100 nM) was added to the culture medium during the treatment/measurement period to stimulate protein degradation. Calcium in the foam of calcium chloride was added to the control and 25-OH VitD₃ treatments so that all the treatments were balanced for calcium. For measurement of protein degradation during the treatment period, leucine free medium was obtained to which [5,5,5]²H₃-leucine was added so that the isotopes of leucine (natural leucine and [1-¹³C]-leucine) could be measured as they were released into the medium through the protein degradation process. The measurement medium was sampled at 2 and 24 h and samples stored at −80° C. until analyzed. The samples were analyzed for leucine using a gas chromatography (model 6890, Hewlett Packard, Palo, Calif.) mass spectrometry (model 5973, Hewlett Packard, Palo, Calif.) and the gas chromatography column used for the analysis was a Zebron ZB-5. (Phenomenex, Torrence, Calif.). Natural leucine, [1-¹³C]-leucine, and [5,5,5²H₃]-leucine were monitored at 302, 303, and 305 AMU, respectively. Corrections for sampling at 2 h and for leucine utilization from the measurement media were made. The amount of the leucine isotopes released was also corrected for utilization (transamination and/or protein synthesis) (96). Concentrations of proteins were analyzed following the microplate assay instructions using a Pierce BCA protein assay kit (Thermo Scientific, Rockford, Ill.). DNA was measured fluorometrically using the Quant-iT™ dsDNA assay kit from Invitrogen (Carlsbad, Calif.).

Statistics

Each cell culture dish was considered an experimental unit for analysis. Data presented are least square means and data were analyzed using General Linear Models in the Statistical Analysis System for Windows (Release 8.02, SAS Institute, Cary, N.C.). Main effects of experiment, HMB, vitamin D, and the interaction of HMB and vitamin D were included in the model. Post-hoc least square means analysis was performed for individual treatment means.

Results and Analysis

After the 24 h treatment period there were no treatment main effects on total protein content in the culture dishes. In FIG. 3, the Protein:DNA ratio (A) and Protein degradation (B) in C2C12 cells treated with Control, 250H-VitD3 (200 ng/mL), HMB (200 μM as Ca(HMB)2-H2O), or the combination is shown. Results presented are least square means of 4 replicate studies. For protein:DNA ratio p-values were 25OH-VitD3=0.34; CaHMB=0.0001; and CaHMB*25OH-VitD3=0.003 and for protein degradation p-values were 25OH-VitD3=0.78; CaHMB=0.33; and CaHMB*25OH-VitD3=0.08. There were no significant treatment main effects for DNA content. Protein:DNA ratio with the combination of HMB and 25-OH VitD₃ (FIG. 3) was significantly greater than either the control group or either treatment group alone and the interaction was significant (p<0.003). This significant interaction response for the main effects would indicate a synergistic response of HMB and 25-OH VitD₃ on protein:DNA ratio. Measures of protein degradation and protein synthesis showed no significant main effects of treatment on protein degradation measured either by natural or [1-¹³C]-leucine release into the medium from the cells. There was, however, a strong trend for the interaction between HMB and 2=50H VitD₃ on protein degradation measured by [1-¹³C]-leucine (p<0.08, FIG. 3). Post-hoc least square means analysis of the effects of HMB alone showed a significant decrease in protein degradation of 7.6 and 6.3% as measured by natural leucine and [1-¹³C]-leucine, respectively (p<0.06). HMB and 25-OH VitD₃ combination treatment also decreased protein degradation, but the lack of neither a significant interaction nor a 25OH-VitD₃ main treatment effect would indicate the effect was due primarily to HMB. Protein synthesis and leucine utilization as measured by disappearance of [5,5,5-²H₃]-leucine from the media showed no differences among treatments. The current series of studies show that HMB and 25-OH VitD₃ combination increases protein:DNA ratio and that HMB decreases protein degradation. These both are indications that the cell is producing more proteins, possibly of a functional nature. The data also show that the HMB decreases dexamethasone stimulated protein degradation in both slower and faster turnover protein pools natural and [1-¹³C]-leucine labels, respectively. Vitamin D tended to decrease dexamethasone stimulated protein degradation in only the faster turnover protein pool. These could indicate that vitamin D affects synthesis of functional proteins as vitamin D has been shown in other cell types to increase cell adhesion proteins (97, 98). In conclusion, the HMB+vitamin D combination was synergistic in increasing protein:DNA ratio in the cells and supports our hypothesis.

Example 4

The amount of Vitamin D administered with HMB must be in an effective amount to raise the blood level of Vitamin D. In this example, it is demonstrated that 500 IU of Vitamin D does not sufficiently raise the blood level of Vitamin D.

Subjects with adequate Vitamin D (plasma 25-OH VitD₃ levels >30 ng/ml) manifested significant improvements in muscle function, while those with biochemical evidence of Vitamin D deficiency (25OH-VitD₃ levels <30 ng/ml) failed to show improvements in muscle strength and functionality. While muscular weakness associated with Vitamin D may not be surprising at classical Vitamin D deficiency levels (blood 25-OH VitD₃ of <15 ng/mL), Bischoff-Ferrari et al continued to see improvement in lower extremity function up to and beyond 40 ng 25-OH VitD₃/mL which are levels well above what previously might have been thought necessary for maximal benefit (11). Therefore, supplementation Vitamin D should be adequate to raise 25-OH VitD₃. FIG. 4 a demonstrates the blood 25-OH VitD₃ response when a control, or supplement containing either 500 or 2000 IU of Vitamin D were given for 12 weeks in older adult over 65 years of age. Subjects supplemented with either the control or 500 IU of Vitamin D for 12 weeks did not increase blood 25-OH VitD₃. Whereas subjects supplemented with 2000 IU of Vitamin D increased blood levels by over 10 ng/mL in 12 weeks. This supplementation established a blood level of 25-OH VitD₃ level >30 ng/ml. FIG. 4 b shows the urine levels of HMB in these subjects. In conclusion, 2000 IU of Vitamin D is sufficient to raise blood levels 25-OH VitD₃, where 500 IU is inadequate. When Vitamin D levels are adequately raised, the use of HMB results in an increase in strength and muscle function.

The foregoing description and drawings comprise illustrative embodiments of the present inventions. The foregoing embodiments and the methods described herein may vary based on the ability, experience, and preference of those skilled in the art. Merely listing the steps of the method in a certain order does not constitute any limitation on the order of the steps of the method. The foregoing description and drawings merely explain and illustrate the invention, and the invention is not limited thereto, except insofar as the claims are so limited. Those skilled in the art who have the disclosure before them will be able to make modifications and variations therein without departing from the scope of the invention.

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The invention claimed is:
 1. A composition comprising a synergistic combination of from about 0.5 g to about 30 g of β-hydroxy-β-methylbutyric acid (HMB) and Vitamin D in an amount sufficient to raise blood levels of Vitamin D to at least about 25 ng/ml, wherein administration of the composition to an animal in need thereof has at least one effect selected from the group consisting of increasing muscle mass, increasing strength and improving muscle function.
 2. The composition of claim 1, wherein said HMB is selected from the group consisting of its free acid form, its salt, its ester, and its lactone.
 3. The composition of claim 2, wherein said salt is selected from the group consisting of a sodium salt, a potassium salt, a magnesium salt, a chromium salt, and a calcium salt.
 4. The composition of claim 3, wherein said salt is a calcium salt.
 5. The composition of claim 2, wherein said ester is selected from the group consisting of methyl esters and ethyl esters.
 6. The composition of claim 2, wherein said HMB is an HMB isovaryl lactone.
 7. The composition of claim 1, where the Vitamin D is in an amount from about 500 IU to about 4000 IU.
 8. The composition of claim 1, wherein said Vitamin D is Vitamin D₃.
 9. The composition of claim 1, wherein said Vitamin D is Vitamin D₂.
 10. The composition of claim 1, wherein the vitamin D is in an amount about 2,000 IU.
 11. The composition of claim 10, wherein the HMB is in an amount about 3 grams.
 12. A composition comprising a synergistic combination of from about 0.5 g to about 30 g of β-hydroxy-β-methylbutyric acid (HMB) and Vitamin D in an amount sufficient to raise blood levels of Vitamin D to at about 25 ng/ml, wherein administration of the composition to an animal in need thereof has at least one effect selected from the group consisting of increasing muscle mass, increasing strength and improving muscle function.
 13. The composition of claim 12, wherein said HMB is selected from the group consisting of its free acid form, its salt, its ester, and its lactone.
 14. The composition of claim 13, wherein said salt is selected from the group consisting of a sodium salt, a potassium salt, a magnesium salt, a chromium salt, and a calcium salt.
 15. The composition of claim 14, wherein said salt is a calcium salt.
 16. The composition of claim 13, wherein said ester is selected from the group consisting of methyl esters and ethyl esters.
 17. The composition of claim 13, wherein said HMB is an HMB isovaryl lactone.
 18. The composition of claim 12, where the Vitamin D is from about 500 IU to about 4000 IU.
 19. The composition of claim 12, wherein said Vitamin D is Vitamin D₃.
 20. The method of claim 19, wherein said synergistic combination of HMB and Vitamin D is administered to said animal in an edible form.
 21. The composition of claim 12, wherein said Vitamin D is Vitamin D₂.
 22. A method for increasing muscle mass of an animal in need thereof comprising the steps of administering to said animal a synergistic combination of from about 0.5 g to about 30 g of β-hydroxy-β-methylbutyric acid (HMB) and Vitamin D in an amount sufficient to raise blood levels of Vitamin D to at least 25 ng/ml, wherein upon said administration of said synergistic combination HMB and Vitamin D to the animal, said muscle mass is increased.
 23. The method of claim 22, wherein said HMB is selected from the group consisting of its free acid form, its salt, its ester, and its lactone.
 24. The method of claim 23, wherein said salt is selected from the group consisting of a sodium salt, a potassium salt, a magnesium salt, a chromium salt, and a calcium salt.
 25. The method of claim 24, wherein said salt is a calcium salt.
 26. The method of claim 23, wherein said ester is selected from the group consisting of methyl esters and ethyl esters.
 27. The method of claim 23, wherein said HMB is an HMB isovaryl lactone.
 28. The method of claim 22, where the Vitamin D is from about 500 IU to about 4000 IU.
 29. The method of claim 22, wherein said Vitamin D is Vitamin D₃.
 30. The method of claim 22, wherein said Vitamin D is Vitamin D₂.
 31. The method of claim 22, wherein said synergistic combination of HMB and Vitamin D is administered to said animal in an edible form.
 32. The method of claim 22, wherein said synergistic combination of HMB and Vitamin D is administered to said animal intravenously.
 33. A method for increasing strength of an animal in need thereof comprising the steps of administering to said animal a synergistic combination of from about 0.5 g to about 30 g of β-hydroxy-β-methylbutyric acid (HMB) and Vitamin D in an amount sufficient to raise blood levels of Vitamin D to at least 25 ng/ml, wherein upon said administration of said synergistic combination of HMB and Vitamin D to the animal, said strength is increased.
 34. The method of claim 33, wherein said HMB is selected from the group consisting of its free acid form, its salt, its ester, and its lactone.
 35. The method of claim 34, wherein said salt is selected from the group consisting of a sodium salt, a potassium salt, a magnesium salt, a chromium salt, and a calcium salt.
 36. The method of claim 35, wherein said salt is a calcium salt.
 37. The method of claim 34, wherein said ester is selected from the group consisting of methyl esters and ethyl esters.
 38. The method of claim 34, wherein said HMB is an HMB isovaryl lactone.
 39. The method of claim 33, where the Vitamin D is from about 500 IU to about 4000 IU.
 40. The method of claim 33, wherein said Vitamin D is Vitamin D₃.
 41. The method of claim 33, wherein said Vitamin D is Vitamin D₂.
 42. The method of claim 33, wherein said synergistic combination of HMB and Vitamin D is administered to said animal in an edible form.
 43. The method of claim 33 wherein said synergistic combination of HMB and Vitamin D is administered to said animal intravenously.
 44. A method for improving muscle function of an animal in need thereof comprising the steps of administering to said animal a synergistic combination of from about 0.5 g to about 30 g of β-hydroxy-β-methylbutyric acid (HMB) and Vitamin D in an amount sufficient to raise blood levels of Vitamin D to at least 25 ng/ml, wherein upon said administration of said synergistic combination of HMB and Vitamin D to the animal, said muscle function is improved.
 45. The method of claim 44, wherein said HMB is selected from the group consisting of its free acid form, its salt, its ester, and its lactone.
 46. The method of claim 45, wherein said salt is selected from the group consisting of a sodium salt, a potassium salt, a magnesium salt, a chromium salt, and a calcium salt.
 47. The method of claim 46, wherein said salt is a calcium salt.
 48. The method of claim 45, wherein said ester is selected from the group consisting of methyl esters and ethyl esters.
 49. The method of claim 45, wherein said HMB is an HMB isovaryl lactone.
 50. The method of claim 44, where the Vitamin D is from about 500 IU to about 4000 IU.
 51. The method of claim 44, wherein said Vitamin D is Vitamin D₃.
 52. The method of claim 44, wherein said Vitamin D is Vitamin D₂.
 53. The method of claim 44, wherein said synergistic combination of HMB and Vitamin D administered to said animal intravenously.
 54. A method for increasing muscle mass of an animal in need thereof comprising the steps of administering to said animal a synergistic combination of from about 0.5 g to about 30 g of β-hydroxy-β-methylbutyric acid (HMB) and Vitamin D in an amount sufficient to raise blood levels of Vitamin D to at about 25 ng/ml, wherein upon said administration of said synergistic combination HMB and Vitamin D to the animal, said muscle mass is increased.
 55. A method for increasing strength of an animal in need thereof comprising the steps of administering to said animal a synergistic combination of from about 0.5 g to about 30 g of β-hydroxy-β-methylbutyric acid (HMB) and Vitamin D in an amount sufficient to raise blood levels of Vitamin D to at about 25 ng/ml, wherein upon said administration of said synergistic combination of HMB and Vitamin D to the animal, said strength is increased.
 56. A method for improving muscle function of an animal in need thereof comprising the steps of administering to said animal a synergistic combination of from about 0.5 g to about 30 g of β-hydroxy-β-methylbutyric acid (HMB) and Vitamin D in an amount sufficient to raise blood levels of Vitamin D to at about 25 ng/ml, wherein upon said administration of said synergistic combination of HMB and Vitamin D to the animal, said muscle function is improved.
 57. A composition comprising a synergistic combination of from about 0.5 g to about 30 g of HMB and from about 500 IU to about 4,000 IU of Vitamin D, wherein administration of the composition to an animal in need thereof has at least one effect selected from the group consisting of increasing muscle mass, increasing strength and improving muscle function. 